1. Field of the Invention
The invention relates to a noise canceller and particularly to technology that can reproduce a waveform of an original signal highly accurately.
2. Description of the Related Art
Japanese Patent Application Laid-Open Publication No. 1994-112853 discloses a noise canceller including: a pulse noise detection circuit that detects pulse noise from a reception signal; a gate control circuit that holds the peak of the detected pulse noise and generates a gate control signal for a predetermined time period if the peak value is equal to a predetermined threshold value or more; and a gate circuit that gates the reception signal during the generation of the gate control signal to remove the pulse noise, and the noise canceller blocks a transmission path from the pulse noise detection circuit to the gate control circuit depending on the detection of the pulse noise. Japanese Patent Application Laid-Open Publication No. 2000-278153 discloses technology that replaces portion including overlapping noises with a signal predicted by forward linear prediction to constrain deterioration of sound quality in an FM receiver.
When the signal is predicted by the forward linear prediction as above, an error is expanded as a time difference is enlarged between a value used for the basis of the forward linear prediction (hereinafter, a basis value) and a predicted value (hereinafter, a forward linear prediction value). For example, in FIG. 9, with regard to a waveform shown in FIG. 9 (waveform shown by a solid line in FIG. 9), when a signal including noise in a section from t1 to t2 is replaced with a signal (a signal shown by a dotted line in FIG. 9) obtained from forward linear prediction values XM+1, XM+2, . . . , XM+N predicted by the forward linear prediction based on basis values X1, X2, . . . , XM to reproduce a signal in the case that the noise is not mixed (hereinafter, an original signal), an error is expanded between the basis values and the forward linear prediction values as the signal approaches t2, and the waveform of the reproduced signal predicted by the forward linear prediction is significantly dissociated from the original signal in the vicinity of t2. Such dissociation deteriorates reproduction quality of an AM receiver, for example.